1. Field of the Invention
The present invention relates generally to metered orifice devices, and more particularly to a fixed metered orifice device for use within PCV systems of internal combustion engines whereby air is introduced into the PCV system in order to control the vapor content within the gaseous stream normally conducted from the engine crankcase to the intake manifold of the engine.
2. Description of the Prior Art
Various products of combustion are produced within internal combustion engines and may include carbon dioxide, carbon monoxide, non-combusted and partially combusted hydrocarbons, oxides of nitrogen and sulphur, and water. The emission of these constituents into the atmosphere by automobiles has contributed greatly to the high levels of air pollution currently being experienced, especially within metropolitan areas. One major source of this emission has been caused by the so-called "blowby" gases which comprise some of the above-mentioned constituents and which are normally forced past the engine pistons and rings and into the engine crankcase. These "blowby" gases are, in turn, mixed with oil vapors containing tars, varnishes, gums, and sludge, which are produced within the crankcase, along with fine oil particles, and the resulting mixture has traditionally been vented from the crankcase into the atmosphere.
In an attempt to reduce such air pollution caused by the emission of these harmful constituents from the engine crankcases, recent legislation has been enacted requiring the passage of such vapors from the crankcase into the engine's fuel-intake system, and this is generally provided for by means of a conduit having a positive crankcase ventilation (PCV) valve disposed therewithin and communicating between the upper region of the engine crankcase, that is, above the oil level, and the engine fuel-intake system. The PCV valve is merely a one-way check valve which allows the crankcase vapors to flow only in one direction, that is, from the crankcase to the fuel-intake system, and this allows for any non-combusted constituents disposed within such crankcase vapors to be recharged into the engines and completely combusted.
Various problems have resulted, however, when utilizing such PCV systems, such as for example, the deposition of tars and sludge within the engine carburetor and/or intake manifold, as well as the upper valve systems, and this particular problem has been only partially remedied by placing a filtering device within the PCV line so as to remove the heavier tars, varnishes, and sludges from the vapor stream. In addition, it is also noted that conventional carburetion equipment is not particularly adapted to effectively mix the additional vaporous combustible products with air so as to provide a highly efficient combustible mixture, and consequently, much of the recirculated mixture is removed from the engine exhaust system in a non-combusted or only partially combusted state.
Still further, it has also heretofore been proposed to incorporate spring-loaded valves within the PCV system which partially restrict the flow of air and vapors through the PCV system when the pressure within the intake manifold drops below a predetermined level. Such devices, have been found to create an excessive amount of suction within the PCV system so as to, in fact, draw oil out of the crankcase, and it is not unusual to find the spark plugs fouled with oil and vapors after the engine has been running at high speeds and then throttled down, due to liquids and vapors being pulled through the system into the cylinders. In addition, the spring-loaded valves themselves become fouled and fail to function properly.
In order to rectify the aforenoted problems, additional atmospherically-vented spring-loaded valves have also been incorporated within the PVC system so as to bleed thereinto a metered or controlled amount of atmospheric air whereby, even when high vacuum conditions exist within the engine intake manifold, the vacuum within the PCV lines leading from the crankcase does not in fact exceed a predetermined maximum. Consequently, such vacuum is insufficient to cause oil or vapors to be sucked out of the crankcase and into the intake manifold. Nevertheless, such additional valves have also become fouled within a relatively short period of time and consequently fail to perform properly.